In recent years, public attention has been attracted to radio-based train control systems in which radio communication is performed between a train and a wireless base station installed along a railroad and operation control and speed control of a train are performed on the basis of information transmitted via the radio communication. The radio-based train control system is more advantages than a train operation control scheme by a conventional fixed block section in terms of an installation cost and a maintenance cost since a track circuit is unnecessary. Further, since it is possible to construct a flexible block section free from a fixed section, it is possible to increase a train operation density, and it is also advantageous in terms of an operation cost.
With the radio-based train control system, there are cases in which an industry science medical (ISM) band is used for radio communication between the ground and a train from a cost perspective because license is unnecessary for the ISM band. However, with the ISM band, other systems, such as a wireless local area network (LAN) or Bluetooth (registered trademark), are widely used, and use of such systems in a train or a rail side building can be a large source of interference for the radio-based train control system. For this reason, with the radio-based train control system, techniques regarding the interference immunity are important technique for performing stable communication.
A technique for implementing high-quality communication in an environment in which there is a lot of interference is disclosed, for example, in Patent Literature 1. This is a technique in which, in orthogonal frequency division multiplexing (OFDM), null symbols are dispersedly arranged in time-frequency slots, interference power is measured in a null symbol with a high degree of accuracy, and a transmission control process and an inter-antenna synthesis process are performed on the basis of the measured interference power.